CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY (DEFICIT) - USD ($) $ in Thousands	Common Stock	Treasury Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss), Net	Total
Balance, beginning at Dec. 31, 2017	$ 29	$ (352)	$ 274,584	$ (265,308)	$ (6)
Balance, beginning (in shares) at Dec. 31, 2017	29,030,757	(33,801)
Increase (Decrease) in Stockholders Equity
Issuance of common stock upon RSU conversion	17,832
Share-based compensation expense			2,053
Net unrealized gain on investments					7	$ 7
Net loss				(29,643)		(29,643)
Balance, ending at Jun. 30, 2018	$ 29	$ (352)	276,637	(294,951)	1	(18,636)
Balance, ending (in shares) at Jun. 30, 2018	29,048,589	(33,801)
Balance, beginning at Dec. 31, 2017	$ 29	$ (352)	274,584	(265,308)	(6)
Balance, beginning (in shares) at Dec. 31, 2017	29,030,757	(33,801)
Increase (Decrease) in Stockholders Equity
Issuance of common stock upon RSU conversion	26,991
Shares issued for exercise of stock options (in shares)	832
Balance, ending at Dec. 31, 2018	$ 50	$ (352)	325,130	(316,983)		7,845
Balance, ending (in shares) at Dec. 31, 2018	49,710,104	(33,801)
Balance, beginning at Mar. 31, 2018	$ 29	$ (352)	275,551	(279,744)	(3)
Balance, beginning (in shares) at Mar. 31, 2018	29,030,757	(33,801)
Increase (Decrease) in Stockholders Equity
Issuance of common stock upon RSU conversion	17,832
Share-based compensation expense			1,086
Net unrealized gain on investments					4	4
Net loss				(15,207)		(15,207)
Balance, ending at Jun. 30, 2018	$ 29	$ (352)	276,637	(294,951)	1	(18,636)
Balance, ending (in shares) at Jun. 30, 2018	29,048,589	(33,801)
Balance, beginning at Dec. 31, 2018	$ 50	$ (352)	325,130	(316,983)		7,845
Balance, beginning (in shares) at Dec. 31, 2018	49,710,104	(33,801)
Increase (Decrease) in Stockholders Equity
Issuance of common stock upon RSU conversion	18,765
Shares issued for exercise of stock options			11
Shares issued for exercise of stock options (in shares)	35,207
Payroll tax withheld for RSU releases			(2)
Share-based compensation expense			1,896
Net unrealized gain on investments					1	1
Net loss				(11,363)		(11,363)
Balance, ending at Jun. 30, 2019	$ 50	$ (352)	327,035	(328,346)	1	(1,612)
Balance, ending (in shares) at Jun. 30, 2019	49,764,076	(33,801)
Balance, beginning at Mar. 31, 2019	$ 50	$ (352)	326,014	(324,583)	(1)
Balance, beginning (in shares) at Mar. 31, 2019	49,756,317	(33,801)
Increase (Decrease) in Stockholders Equity
Issuance of common stock upon RSU conversion	7,759
Payroll tax withheld for RSU releases			(1)
Share-based compensation expense			1,022
Net unrealized gain on investments					2	2
Net loss				(3,763)		(3,763)
Balance, ending at Jun. 30, 2019	$ 50	$ (352)	$ 327,035	$ (328,346)	$ 1	$ (1,612)
Balance, ending (in shares) at Jun. 30, 2019	49,764,076	(33,801)